All present methods of bathroom deodorising either cover up the bad air (aerosol perfume spray) or try to increase air replacement (exhaust fans). Variations include perfume dispensers located around the toilet rim activated by the flush, toilet "blue" in the holding tank which foams slightly after flushing. However, the foam is produced after the odour has already been released and after the fecal matter is flushed away.
The cistern is an attempt to prevent the spreading of odours by trapping the human waste under the water for the period before it is flushed away. They cannot work as designed because more fibre in the Western diet makes faeces float on top of the water, facilitating transfer of odours to the surrounding air.
Portable chemical toilets partly solve the problem by using liquids that are lighter than water, increasing the likelihood of solid waste sinking and being isolated. Some use a spring trapdoor which re-closes after defecation to isolate collected waste. These options are not appropriate for the bathroom.
There are certain natural non-flushing toilets which use a permanent fan to produce negative pressure under the seat. They are very effective in eliminating smells from the bathroom but are more for rural settings since they transfer the smell outside.
There is a need for using an airlock to isolate human waste from the surrounding air in the bathroom.